MINNEAPOLIS—The mystery of Tsuyoshi Nishioka may never be solved.
The former Japanese batting champion, signed to a three-year, $9 million contract by the Twins before the 2011 season, was outrighted from Minnesota's 40-man roster in August, making it unlikely he will ever appear in another major league game.

"The player we all saw was not the player we scouted in Japan. For whatever reason, we haven't seen that guy," vice president for player personnel Mike Radcliff said. "I mean, none of us believed that he wouldn't hit."

Certainly not after Nishioka, 28, led Nippon Professional Baseball with 206 hits and a .346 average in 2010. The Twins ponied up a $5 million posting fee to secure the switch-hitting infielder's rights.

His performance in the U.S. has been disastrous. He started off the 2011 season by colliding with Yankees outfielder Nick Swisher while trying to turn a double play. He returned two months later, batted just .226/.278/.249, and was error-prone at shortstop and second base.

Sent to Triple-A Rochester to start this season, Nishioka appeared to be making gradual progress. He was recalled on Aug. 6, however, and his second chance went even worse than his first. He was shaky in the field and went 0-for-12 in three games before getting outrighted, amid speculation the Twins will try to sell him to a Japanese team over the winter.

"Players coming over from another country, a player like Ichiro could adjust in his first year. But players like myself kind of struggle to do that," he said. "For some players, from any country, it takes time to adjust."

TWIN KILLINGS

• The Twins extended their player-development contracts with Rochester, their Triple-A affiliate since 2003, and New Britain, their Double-A affiliate since 1995.